Biomonitoring of elements airborne pollution in European Mediterranean region by two Tillandsia species

Tillandsia genus belongs to the Bromeliaceae family plants and some species display active or passive biomonitoring capacities in their natural habitat as it has been described mostly in the American continent. However, Tillandsia aeranthos (Loisiel.) Desf. and Tillandsia bergeri Mez have never been studied for their metal air pollution biomonitor potential. A recent study conducted in our laboratory brought to light the maximum capacity of elements bioconcentration into these two species leaves. The aim of the present study is to determine if T. aeranthos and T. bergeri acclimated to Southern/European region are good biomonitors for airborne elements pollution. Twelve elements were chosen to evaluate the biomonitoring potential (As, Ba, Co, Cr, Cu, Fe, Mn, Ni, Pb, Sn, Ti and Zn). After sampling, the content of the twelve elements in leaves was measured by Inductively Coupled Plasma-Optical Emission Spectrometry and Inductively Coupled Plasma-Mass Spectrometry. Data sets were treated according to sampling sites by box plots over time and Principal Component Analysis. The results showed differences between the two species, with T. bergeri possessing a higher capacity in accumulating elements than T. aeranthos. Fe, Zn and Co showed a higher contribution in the accumulation process in the two Tillandsia species leading to the hypothesis of a good affinity of the two species with these elements. Values obtained for five elements (As, Cr, Ni, Pb and Zn) were compared with values recorded by a monitoring station close to sampling sites showing the efficiency of these two Tillandsia species as biomonitors. High Co accumulation rates obtained in both Tillandsia species were particularly intriguing but could not be rationalized as this metal is not currently monitored by air pollution station in this region. T. aeranthos and T. bergeri proved their efficiency for the biomonitoring of elements air pollution, especially for Co, Fe and Zn.